The present invention relates to a process and apparatus for rectifying air in a single column to produce oxygen. More particularly, the present invention relates to such a process and apparatus in which the single column operates at an above-atmospheric pressure to produce the oxygen at an above-atmospheric delivery pressure.
The prior art has provided a variety of processes and apparatus to rectify air within various single column arrangements to produce an oxygen product. In a typical single column oxygen producing plant, air is compressed, purified, cooled to a temperature suitable for its rectification and then introduced into a heat exchanger in the bottom of the column to provide boil-up against the partial liquefaction of the air. The air is thereafter introduced into the column, at an intermediate location thereof. The air is distilled in the column to produce a liquid oxygen column bottom and a nitrogen vapor tower overhead. The column typically operates slightly above atmospheric pressure. As a result, the liquid oxygen must again be pumped to increase its pressure to a delivery pressure. As can be appreciated, such pumping represents an energy outlay which adds to the operating overhead involved in producing the oxygen product.
As will be discussed, the present invention provides a process and apparatus in which air is distilled in a column to produce an oxygen product at an above-atmospheric delivery pressure without the necessity of there being any additional energy outlay involved in increasing the pressure of the oxygen product to the delivery pressure.